Guy Norris/LOS ANGELES
General Electric expects borescope inspections of 28 GE90 engines to be completed by 5 April following the failure of a low pressure turbine (LPT) of an engine on a British Airways Boeing 777-200IGW at London Heathrow on 12 March. The incident caused serious disruption at Heathrow as part of a runway had to be closed to enable debris to be cleared.
The failure occurred when a misaligned guide vane section worked its way aft and made contact with the LPT. The event surprised GE, which had already identified the condition during development tests and had changed the assembly process that led to the problem.
The problem was created when the LPT was married to the turbine centre frame on which the first stage vanes are located. "It's a big module and it has got to be aligned carefully," says GE. "The process led to the 12 o'clock vane segment being displaced aft. In this case, it seems the section worked itself aft and after roughly 3,000h finally contacted the blade," says the engine maker.
Although the assembly process was changed and all engines, including zero time units, were inspected for displaced vane segments, the BA engine appears to have slipped through the GE screening process.
By the end of March, 60% of the 28 engines involved had been inspected and "every one was clean" says the manufacturer.
"BA, along with GE, is doing expedited inspections at the rate of one per day fundamentally. The aircraft continued to operate with borescope inspections performed overnight or during routine maintenance," says GE.
Air France accepted the first of 10 GE90-powered 777-200IGWs on 29 March. The French carrier will take a further two aircraft in April. Kuwait Airways also received the first of two GE-powered 777s on 30 March.
Source: Flight International
